1. Field of the Invention
The invention relates to the consumption of dietary fibers to prevent the occurrence or recurrence of colon polyps and to prevent colon cancer.
2. Background Art
Observational epidemiological studies and clinical experiments have generated a number of hypothesis about the role of dietary factors in the etiology of colorectal cancer: fat and meat, especially beef, may enhance the risk, while fiber, cruciferous vegetables, lactose and vitamins C and E may protect.
According to Lineback et al., "Food Carbohydrates", (1982), page 296, there is not any completely satisfactory definition of the material which is generally referred to as fiber. The indigestible matter in animal feeds has always been designated as "crude fiber", and the term "dietary fiber" has been suggested for the plant cell wall constituents that are not digested by the secretion of the human digestive tract. The current definition of dietary fiber is not entirely satisfactory. There is a distinction between crude fiber and dietary fiber, since the former is a designation of a fraction determined analytically in a manner that gives an approximation of only cellulose and lignin and not of other cell-wall constituents not digested by man.
The substance that the lay public most readily equates with the term dietary fiber is wheat bran. Wheat bran is a heterogeneous substance which contains, in addition to fat and protein, at least 15 different minerals ranging from phosphorus and potassium at 1.04 and 1.38 percent, respectively, to iron (122 ppm), manganese (80 ppm), silicon (.+-.ppm) and selenium (0.1 ppm). Burkitt, D. P., "Epidemiology of cancer of the colon and rectum", Cancer 28, 3, (1971); Burkitt, D. P., "Colonic-rectal cancer: fiber and other dietary factors", Am. J. Clin. Nutr. 31, S58, (1978), and Trowell, H., "Ischemic heart disease and dietary fiber", Am. J. Clin. Nutr. 25, 926, (1972), concluded from epidemiological observations that populations subsisting on high residue diets exhibted fewer of the diseases of Western civilization (cancer, heart disease and, gallstones). Cleave, T. L., "The neglect of natural principles in current medical practice", J. R. Nav. Med. Serv. 42, 55, (1956), suggested that modern day diseases were due to increasing intake of refined flour and sugar. It must be remembered that Burkitt and others were referring to a type of diet rather than a single component.
Epidemiologic studies have identified a low intake of dietary fiber as one of the factors associated with an increased rate of cancer of the colon [for example, see "Dietary fibre, transit time, faecal bacteria, steroid and colon cancer in two Scandanavian population", International Agency for Research on Cancer, Intestinal Microbiology Group, Lancet, July 30: 207-211, (1977), and Wynder, E. L., "The environment and cancer prevention", J. Environ. Path. Toxicol. 3: 171-192, (1980)]; other such studies include high intake of fat and animal protein [for example, see Armstrong, B., et al., "Environmental factors and cancer incidence and mortality in different countries with special reference to dietary practices", Int. J. Can., 15: 617-631, (1975)].
Different methods of estimating fiber consumption have lead to different conclusions about its association with national mortality: Lui, K., et al., "Dietary cholesterol, fat and fibre and colon-cancer mortality", Lancet, 782-785, (Oct. 13, 1979), found a negative association, while Draser, B. S., et al., "Environmental factors and cancer of the colon and breast" British Journal of Cancer, 27, 167, (1973), did not find such a negative association.
Retrospective studies designed to compare the dietary habits of colon cancer patients with controls have also failed to provide consistent evidence on the fiber hypothesis. Several of the studies have supported it [Bjelke, E., "Case control study of cancer of the stomach, colon and rectum", In Oncology (1970) Eds. R. L. Clarke, R. W. Cumley, J. E. McCay and M. M. Copeland. Proceedings of the 10th International Cancer Congress, Volume V, Chicago, Ill.: Year Book Medical Publishers Inc., (1971), p. 320; Modan, B., et al., "Low-fibre intake as an etiological factor in cancer of the colon", Journal of the National Cancer Institute, 55, 15, (1975); Graham, S., et al., "Diet in the epidemiology of cancer of the colon and rectum", Journal of the National Cancer Institute, 61, 709, (1978); and Dales, L. G., et al., "A case-control study of relationships of diet and other traits to colorectal cancer in American blacks", American Journal of Epidemiology 109 (2), 132-144, (1978)], while others have not [Higginson, J., "Etiological factors in gastrointestinal cancer in man", Journal of the National Cancer Institute, 37 (4), 527-545, (1966); Wynder, E. L., et al., "Environmental factors of cancer of the colon and rectum", Cancer 20, 1520-1561, (1967); and Jain, M., et al., "A case-control study of diet and colorectal cancer", International Journal of Cancer, 26, 757-768, (1980)].
Concerning the incidence of colon cancer seen in industrialized populations which has been associated with lack of dietary fiber, the presence of fiber in the intestinal tract decreases transit time, which reduces contact time between potential carcinogens and the mucosa, and it dilutes the intestinal contents and thus reduces the possibility of interaction of procarcinogens with bacteria. Although some epidemiological data would appear to bear out the above stated hypothesis, some investigators, working from the same data base, have found little correlation between dietary fiber but a strong correlation with ingestion of animal fat. However, a high fiber diet is usually a low-fat diet and vice versa.
Experimental studies have shown that some kinds of fiber can protect against chemically induced cancer. Rats fed stock diets had fewer 2-acetylaminofluorene-induced tumors than those fed semipurified diets. Colon cancer can be induced in rats by several compounds, including 1,2-dimethylhydrazine, methylnitrosourea and azoxymethane. Wheat bran has been found to protect rats against colon tumors induced by either injection [Fleiszer, D., et al., "Protective effect of dietary fibre against chemically induced bowel tumors in rats", Lancet 2, 552 (1978)] or oral administration of 1,2-dimethylhydrazine [Barbolt, T. A., et al., "The effect of bran on dimethylhydrazine-inducedcolon carcinogenesis in the rat", Proc. Soc. Exp. Biol. Med. 157, 656, (1978)]. In Watanabe, K., et al., "Effect of dietary alfalfa, pectin and wheat bran on azoxymethane or methylnitrosourea-induced colon carcinogenesis in F344 rats", J. Natl. Cancer Inst. 63, 141, (1970), rats were fed 15 percent alfalfa, pectin or wheat bran and the effects of an injected carcinogen (azoxymethane) in one group were compared with one administered by intrarectal instillation (methylnitrosourea) in another. Pectin and bran protected against azoxymethane-induced tumors but not against methylnitrosourea. Alfalfa did not affect the course of azoxymethane-induced tumors but significantly increased the incidence of methylnitrosourea-induced tumors. The data indicates that the action of dietary fiber was mediated by the mode of administration of the carcinogen.
The decreased intake of dietary fiber has been implicated as a factor in diseases such as cancer, diabetes and coronary disease. In the case of diabetes, increased dietary fiber definitely lowers plasma glucose and insulin levels. Data relating to heart disease and colon cancer are not as clear cut and must be assessed in the light of differences in total diet and lifestyle between populations at high and low risk. (Lineback et al., ibid., page 306.)
"FDA Studies Advertising For Kellogg's All-Bran--Linked to Cancer Prevention", The Washington Post, (Nov. 6, 1984), pages E1 and E4, states:
"The Food and Drug Administration has launched a preliminary review of a new advertising campaign by the Kellogg Co. that links its All-Bran cereal to cancer prevention." PA0 "The Kellogg ad campaign is the first by a major food manufacturer to specifically link its product to cancer prevention, a claim the FDA fears may violate federal rules. Under FDA regulations, it is illegal to make health claims about specific foods without prior FDA approval." PA0 "`Is this promotion, in its language, offering a drug because of the product's linkage to the disease called cancer?` said FDA spokesman Bruce Brown. If so, then Kellogg has failed to win FDA approval of All-Bran as a way to prevent cancer, Brown added." [p. E-1] PA0 "However, Kellogg's All-Bran Advertisement represents the first time a major manufacturer has gone a step further and cited the quality of a specific food--in this case high fiber--as a way to prevent a specific disease." PA0 "As a result, federal regulators say they are faced with a serious problem. On the one hand, Brown noted, they applaud Kellogg for bringing vital health information to the public. For the ad clearly points out that the `National Cancer Institute believes a high fiber, low fat diet may reduce your risk of some kinds of cancer.`" PA0 Nonetheless, Brown said, the claims may ultimately be considered misleading by federal regulators because it not include enough information. Although the promotion encourages consumers to eat All-Bran, it may give the impression that all consumers need to do to prevent cancer is to eat All-Bran." PA0 "That it has apparently angered California's Cancer Advisory Council, which, under the auspices of the state's Department of Health Services, is currently drafting a letter to the FDA." PA0 "State officials declined to talk about the letter, saying it was premature to discuss it since it had not been approved and mailed yet. Advertising Age, however, noted that the cancer advisorycouncil was disturbed because there is no scientific proof that All-Bran prevents cancer." PA0 "Kellogg officials, however, said that all they were trying to do was work with the National Cancer Institute to publicize the cancer awareness prevention project. `We want to communicate the NCI report that says that a high fiber, low fat diet may reduce your risk of some kinds of cancer,` said Celeste Clark, director of corporate publicity. `This is the first time Kellogg has mentioned cancer in its advertisements . . . We worked very closely with NCI in developing the advertising message.`" [Emphasis supplied][p. E-1 and p. E-5] PA0 "Among the possible objections FDA could have, Brown said, was that there are many different types of cancer. Kellogg implies high-fiber is a good way to prevent all types of cancer." PA0 "Additionally, Brown said, the claims don't say how to use All-Bran if it really is to prevent cancer." [p. E-5] PA0 "Following the reawakening interest in dietary fiber, the physiological as well as technological aspects of materials considered suitable supplements for fiber-enrichment in various food formulations have become the subject of many investigations. Attempts have been made to draw conclusions as to the relationships between the type of dietary fiber and its functional behavior under varying processing conditions. Because of the high individuality of the test material, drawing of generally valid conclusions proved to be a very difficult task. It is now recognized that a thorough physical and chemical characterization of the fiber-rich material must preclude any valid prediction regarding its functional or physiological effects (Parrott and Thrail 1978)." PA0 "We are thus approaching the more advanced phase of research in this field, in which attempts are being made to relate the functionally relevant physical and physicochemical properties of dietary fiber to its detailed chemical profile, rather than to its total content or distribution of more or less arbitrarily defined fractions. There is still a great deal of ambiguity surrounding these relationships. Great complexitiy of the studied material, lack of uniform methodology, high risk of creating artifacts under in vitro conditions and disreprancies between in vitro and in vivo situations are mostly responsible for a hitherto unsatisfactory status of our knowledge on this subject." [Emphasis supplied] [pages 333 and 334] PA0 (a) about 40 to about 70 weight percent of bran flour; PA0 (b) about 20 to about 50 weight percent of whole wheat flour; PA0 (c) about 5 to about 15 weight percent of rice flour; PA0 (d) about 0.5 to about 3 weight percent of calcium carbonate; PA0 (e) about 0.03 to about 0.005 weight percent of reduced iron; and PA0 (f) about 0.1 to about 0.005 weight percent of riboflavin.
Physiological effects of dietary fiber ought to be neither simple nor uniform, because the human gastrointestinal tract can accommodate to altered conditions and shows large variability in its actions. It has been postulated that beneficial effects of fiber in the large intestine include a binding and dilution of injurious substances. Although food remnants in the human large intestine are thought to provide little if any direct nutrition, they serve as substrates for microflora.
Lineback et al., ibid., states:
There are some potential disadvantages to the use of dietary fiber. Fiber-rich diets appear to induce malabsorption of minerals. Another potential hazard of fiber is in respect to reduce energy intake and protein utilization. Other possible deleterious effects of fiber such as persorption or volvulus of the sigmoid colon do not seem to be an immediate problem in populations ingesting normal, well-balanced diets.
In the case of colorectal cancer, colorectal polyps might be a suitable precursor of malignant disease. There is evidence for the causal association of adenomatous polyps and adenocarcinoma of the colon. Briefly, the prevalence of adenomatous polyps in several countries follows the incidence of colon cancer.
Allen, L. M., "Calciium bioavailability and absorption: a review", Am. J. Clin. Nutr. 35: 783-808, (1982), discussed the question of the adverse effect of bran intake on calcium bioavailability. Particular reference was was made in Allen to Cummings, J. H., et al., Am. J. Clin. Nutr. 32: 2086, (1979), which described the creation of a negative calcium balance in a few controlled subjects on a high bran diet.
U.S. Pat. No. 1,173,932 (Cockrell) discloses a cereal breakfast food consisting of about 60 percent of wheat bran and the remainder corn meal and oats flour, the latter two items being added to make the bran more palatable. The bran is used for its laxative properties.
U.S. Pat. No. 1,210,589 (Black) discloses a bran biscuit or cake which contains shredded cereal and syrup for nutrition and to make the bran palatable. The shredded cereal can be corn, wheat or rice. About 371/2 percent of bran is used in the formula. Black mentions that bran has laxative properties.
U.S. Pat. No. 1,244,586 (Cockrell) discloses a cereal breakfast food consisting of about 60 percent of wheat bran and the remainder corn meal, wheat and oats. The bran is used for its laxative properties.
U.S. Pat. No. 1,263,609 (Schuyler) discloses a self-rising pancake flour which contains ground rice bran, baking powder, wheat flour, soy flour, rice polish and salt. The mixture can include rice flour. The given example uses 22.5 percent of ground rice bran. The bran is used as a flavorant.
U.S. Pat. No. 1,271,139 (Dickerson) discloses a composition which includes bran (e.g., 15 percent), whole wheat flour, wheat flour, rye flour, etc. The composition is used to make biscuits.
U.S. Pat. No. 3,062,659 (Vollink) discloses an extrusion-cooked, ready-to-eat breakfast cereal flakes which can contain rice flour or bran. A moist comminuted starch-containing cereal mixture is passed through a cooker extruder, the expanded extrudate is tempered and then the cereal material is flaked and toasted. Example 2 uses a starting formula that includes 60 percent of ground whole wheat and 24 percent of bran.
U.S. Pat. No. 4,327,116 (Weith) discloses a bran bakery product from dough composed of 100 parts by weight of bran, 200 to 300 parts by weight of water and 2.5 to 15 parts by weight of carob bean flour (or other vegetable thickening agent). Other conventional dough ingredients such as flavoring agents can be used. Weith specifically mentions wheat bran and rye bran. The prior art section of Weith states that cereal fibers are used as casual therapy of obstipation and intestinal diseases.
U.S. Pat. No. 4,350,714 (Duvall) teaches a corn bran, extrusion-cooked, expanded cereal which further contains corn flour, oat flour, ground limestone, [i.e., CaCO.sub.3 ], sugar, salt, soda, vitamin premix and colorant. Duvall states that wheat flour and rice flour can be present. Example 1 shows the use of 25 percent of corn bran flour, and the claims recite that sufficient ground corn bran is used to provide 3.5 to 10 weight percent of fiber. The extruded pieces are enrobed in a syrup which includes sugar, coconut oil and water.
British Pat. No. 1,561,190 (Weetabix) discloses a food mixture containing bran and a binding agent (starchy material or gum) is mixed with water. The mixture is extrusion cooked. The mixture (on a dry basis) contains 10 to 95 percent of bran. The mixture can also contain wheat and rice flours.
German O. S. No. 2,837,294 (Bories et al.) discloses an extrusion cooked foodstuff composed of bran, 20 to 80 percent gluten, 5 to 20 percent, and the balance flour or starch, with the addition of 5 to 20 percent water after charging the mixture to an extruder.
Known foods containing bran include bran muffins and cereals, such as, All Bran, 100% Bran, Shreddies, Bran Flakes and Bran Crunchies. Wheat bran is found naturally in whole-wheat breads and cereals, can be bought separately for adding to other foods and is rich in dietary fiber.